<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>输入框的布局</title>
</head>
<style>
  .InputAddOn {
    display: flex;
  }

  .InputAddOn-field {
    flex-grow: 0;
    flex-shrink: inherit;
    flex: 1;
  }
</style>
<body>
  <div class="InputAddOn">
    <span class="InputAddOn-item">文本</span>
    <input class="InputAddOn-field">
    <button class="InputAddOn-item">搜索</button>
  </div>
  
</body>
</html>